Pulse welder and method of using same

ABSTRACT

An electric arc welder for performing a pulse welding process by a current between an advancing electrode and workpiece where the welder comprises a short detecting circuit for creating a short signal upon occurrence of a short circuit between the advancing electrode and the workpiece and a boost circuit to create a plasma boost pulse after the short circuit is cleared during the time period when the welder is not outputting the peak pulse current.

The present invention relates to a novel electric arc welder and moreparticularly to an electric arc welder for performing a novel pulsewelding process and the method of pulse welding using the novel arcwelder.

BACKGROUND OF INVENTION

In electric arc welding, one of the most popular welding process ispulse welding which primarily uses a solid wire electrode with an outershielding gas. MIG welding utilizes spaced pulses which first melt theend of an advancing wire and then propel the molten metal from the endof the wire through the arc to the workpiece. Under ideal conditions, aglobular mass of molten metal is melted and transferred during eachpulse of the pulse welding process. An interruption in the normaloperation of a pulse welding process occurs when the molten metalcontacts the workpiece before being released from the advancing wire.Consequently, the high voltage pulse welding of over 25 volts isnormally used so that the gap between the end of the electrode and thewire is relatively large. This limits the incidence of short circuitsand the resulting spatter and puddle disturbance. It is advantageous tohave a small gap or arc length less than about 0.20-0.30 inches.However, pulse welding usually requires a substantially higher voltageto assure proper transfer of the molten metal and to reduce shortcircuits. Nevertheless, the pulse welding process invariably involves ashort circuit condition which must be eliminated rapidly to obtain theconsistency associated with proper pulse welding. To remove shortcircuits, it is well known to increase the arc current immediately upondetection of the short circuit. The high arc current causes anelectrical necking action to immediately separate the molten metal fromthe advancing electrode to again establish the arc. A discussion of thiswell known concept is contained in Ihde U.S. Pat. No. 6,617,549incorporated by reference herein. Even with this well known shortcircuit clearance procedure, high voltage is still required for solidwire and the travel rate of the wire must be fairly low. When attemptingto use cored wire for pulse welding, the arc voltage must be maintainedfairly high, well above 25 volts, to avoid short circuit conditions thatare not desired in a pulse welding process. In summary, short circuitscause reduced quality of the weld and reduce the traveling rate of thewelding operation, as well as requiring high voltage with itsdisadvantages. These short circuits are more troublesome when attemptingto use the metallurgical advantage of metal cored electrodes.

Short circuits in a pulse welding process affects arc stability,especially at lower voltages where the average arc length is less thanabout 0.20-0.30 inches. They also cause spatter during breaking of theshort circuit. Consequently, pulse welding requires a procedure forclearing of inadvertent, random short circuits. This was done by merelyincreasing the arc current until the short circuit was cleared. Thus,the pulse welding process required high voltages, greater than 25 volts,to minimize inadvertent short circuits. This resulted in the need tooperate at lower travel speeds. Furthermore, spatter and non-uniformweld beads resulted when high voltages and normal short circuit clearingwas employed.

Pulse MIG welding primarily uses a solid wire electrode, metal coredwire, or flux cored wire typically shielded with an outer shielding gas.The power source creates a special pulsed output that alternates betweena high output, sometimes called the “peak” and a lower output, calledthe “background.” The peak output is greater than the weldingelectrode's spray transition current for a duration long enough to formand transfer one droplet of metal from the advancing electrode to theworkpiece. Between pulses, the lower background output allows theelectrode to advance toward the workpiece and be repositioned in orderfor the next peak to deposit the next droplet. Under ideal conditions,the pulsed output is maintained such that one droplet transfers from theelectrode to the workpiece for each peak without allowing the droplet tobridge the gap causing a short circuit. This condition can be achievedwhen a sufficiently long arc length is maintained producing a relativelyhigh average arc voltage. For example, pulse welding with a steelelectrode running under 90% argon, 10% CO₂ is performed with an averagevoltage greater than about 26 volts.

In practice, there are many advantages when operating a welding process,such as pulse welding at shorter arc lengths. These advantages includelower heat input and better control of the puddle at higher travelspeeds. At reduced arc lengths, partially transferred droplets are moreapt to bridge the gap between the electrode and the work causing shortcircuits. As the arc length is reduced, shorting events become morefrequent and become harder to clear. Modem pulse welding power sources,such as the POWERWAVE by Lincoln Electric contain a technique to clearshort circuits. When a short circuit is detected, the machine's outputis increased in a controlled fashion until the short circuit is“pinched” off and the short is cleared. A discussion of this well-knownconcept is contained in Kawai U.S. Pat. No. 4,889,969, and in Ihde U.S.Pat. No. 6,617,549 incorporated by reference herein. Using thiswell-known technique, the welding process will remain stable even whileoccasional short circuits occur. This method allows users to reduce thearc length yet maintain stable operation at lower heat input levels.This improves the fast follow characteristics at higher travel speeds.For the previously cited example, the stable operation point is reducedto a voltage greater than about 23 volts. As the arc length is reducedbelow this point, shorting events occur quite frequently and may requirea significant increase in pinch current in order to break shorts. Whenthe short does break at high current, spatter typically occurs and anaccompanying instability will follow as the high current pushes down onthe puddle causing an oscillation. This problem is sometimes caused byrepetitive shorting. As a short is cleared, another short immediatelyforms and is difficult to clear.

Cored wires are wires that are comprised of a metal sheath containing acore of metal power and/or slag producing compounds (FCAW-G) and/orcompounds that produce shielding gases (FCAW-S). These wires are veryadvantageous to produce the desired metallurgy of the weld metal and toprotect from contamination. Many of these cored wires can be used in apulse welding process in a fashion similar to solid wires. However, inuse of solid wires, these cored wires exhibit an increase in thefrequency and severity of short circuits as the arc length is reduced.Indeed, the minimum arc length required for cored wires is higher thanthe minimum arc length or voltage for a solid wire since pulsing coredwires tends to melt the sheath leaving the core exposed allowing it todip into the puddle. Thus, the advantage associated with coredelectrodes can not be fully employed. There is a need for a pulse welderthat can use cored electrodes with a reduced voltage without the problemof repeated short circuiting or where such shorts are clearedefficiently to eliminate their adverse impact.

THE PRESENT INVENTION

The present invention relates to an electric arc welding and method ofusing the same which performs a pulse welding procedure where a shortarc length (less than 0.10 inches) or a low voltage of 17-22 volts canbe used to control the puddle and prevent arc from skipping ahead of thepuddle. Furthermore, the travel speed is increased with the use of alower arc length and, thus, lower voltage without promoting shorting aspreviously described. The use of the present invention ensures thatshorting occurs at low background current. This avoids spatterassociated with a high current when entering a short and high currentwhen exiting a short. The present invention ensures reliable separationof the wire tip and the puddle surface, even with small arc lengths.This enhances rhythm and stability in the high current pulse and in thelow background current cycle. The invention is designed for high speedautomatic welding of the type performed by a robot where a low voltage,short arc length is obtainable so that the travel speed can beincreased. The invention improves low voltage welding at high speeds asit stabilizes the shortened arc length and thus reduces spatter. Inaccordance with the present invention, a short circuit in the pulsewelding process is detected and cleared in accordance with standardtechnology; however, after the short circuit is cleared, a plasma boostpulse is created. This boost pulse is a high current pulse with power inthe range of 5-20 KW and preferably in the range of 10-20 KW ofregulated power. When using the invention for ferrous metal welding, thepower of the plasma boost pulse is generally over 5 KW; however, whenwelding aluminum the plasma boost pulse can be reduced to 1.0-2.0 KW.Thus, the practical range is 1.0 KW to about 20 KW. This high currentplasma boost pulse increases the output arc current at separation of theshort circuit. This boost pulse increases the arc force to push thepuddle away from the electrode, so that another short circuit does notoccur during the same cycle. The plasma boost pulse heats the end of theelectrode rounding the end of it to about the size of the wire diameterand an increase in arc force creates a separation between the wire andpuddle so the electrode does not immediately short again. After theshort has been cleared and the plasma boost has increased the arc forcefor a short period of time, generally in the range of 0.2-5.0 ms, theweld process is continued. The low background current of the pulsewelding process allows the droplet to be pushed closer to the puddlebefore the next pulse transfers the formed droplet into the puddle. Theinvention involves the provision of a current, voltage or power pulseafter the short circuit condition has been cleared using a standardshort circuit clearing procedure used in many welders. This stabilizesthe weld puddle and immediately allows resumption of the normal pulsewelding process so that a high voltage and low speed is not required forthe process. Even though the electric arc welder and method are designedbasically for automated applications with high travel speed and lowvoltage, the invention is also used for semi-automatic applicationswhere penetration must be reduced and is advantageous for cored wires,where high travel speed is required. It has also been applied to pulsewelding using flux cored wire. The plasma boost pulse is similar to theSTT peak current pulse in that it creates a droplet on the end of theelectrode and forces the puddle from the electrode. The STT weldingprocess has been pioneered by The Lincoln Electric Company and isdisclosed in several patents, such as Parks U.S. Pat. No. 4,866,247,incorporated by reference herein as background information. The STTprocess has a waveform intentionally creating a short circuit. The useof a plasma boost pulse immediately after the clearance of a shortcircuit does not constitute a generated portion of the waveformconstituting the actual pulse welding process. A short circuit is arandom event that is not detrimental when using the present invention tocontrol the puddle when the short circuit is cleared so the next shortcircuit will be later in the process. The plasma boost is created duringan interrupt in the normal pulse welding process to stabilize thepuddle, reduce spatter and increase welding speed, while allowing lowvoltage operation for both solid metal electrodes and cored electrodes.By using the invention, short circuits caused by the drastically reducedvoltage (i.e. arc length) are not process disruptive. In practice, thewelder is one using waveform technology pioneered by The LincolnElectric Company of Cleveland, Ohio. The pulses and background currentportions are formed by a high switching speed power source as smallpulses created at a rate of over 18 kHz with a profile controlled by awaveform generator.

In accordance with a further aspect of the invention, the plasma boostpulse is preceded by a novel short circuit clearing process similar tothe STT process. When a short circuit is detected, the arc current isreduced and then allowed to increase along a pinch pulse profile with afirst abrupt slope and then a more gradual slope. A premonition circuit,normally a dv/dt detector is actuated when the short circuit is ready to“neck” or break. Then the arc current is dropped to a low level toreduce spatter. This terminates the short circuit and provides smoothsurface tension transfer so the short circuit is really an excellentprocedure for transferring metal to the workpiece. When there is an arcor plasma condition, the plasma boost pulse of the invention isoutputted by the welder. This is a practical procedure for clearing theshort circuit in a pulse welding process and is novel when incombination with the other advances of the present invention.

In accordance with the present invention, there is provided an electricarc welder for performing a pulse welding process by a voltage drivencurrent between an advancing electrode and a workpiece. The current canbe controlled by voltage or current regulation. The welder comprises ashort detecting circuit creating a short signal upon occurrence of ashort circuit between the advancing electrode and the workpiece andboost circuit to create a plasma boost pulse after the detection of ashort circuit. In the preferred embodiment of the invention, there is astandard short circuit clearing circuit that increases the arc currentafter the short circuit signal and before the plasma boost pulse. Thisremoves the short circuit before the plasma boost pulse. The plasmaboost pulse has a regulated power in the general range of 1.0 KW to 20KW and more particularly in the range of 10-15 KW. The plasma boostpulse has a duration in the general range of 0.2-5.0 ms. The inventionis quite useful when welding with a cored wire electrode, such as metalcored and flux cored wire electrodes.

In accordance with another aspect of the present invention, the plasmaboost pulse occurs during an interrupt in the normal waveform generatorthat creates the waveforms constituting a pulse welding process.

In accordance with yet another aspect of the invention, the boostcircuit for creating the plasma boost pulse of the pulse welding processalso includes the creation of a controlled background current followingthe plasma boost pulse. This background current is normally differentfrom the background current of the pulse waveform and continues untilthe next generated pulse in the pulse welding process. The end of thegenerated background segment resets the timer to initiate the standardpulse wave process. The background segment is adjustable in someinstances by a voltage feedback from the output arc voltage of thewelding process. The arc voltage created during a specific plasma boostpulse controls the background segment following that specific plasmaboost pulse.

In accordance with another aspect of the invention there is provided amethod of pulse welding by a series of pulses between an advancingelectrode and a workpiece. The method comprises detecting a shortcircuit between the electrode and the workpiece and then creating aplasma boost pulse after the short circuit. In accordance with thepreferred embodiment, the plasma boost pulse occurs after the shortcircuit has been cleared in accordance with standard technology.

In accordance with still another aspect of the present invention, aplasma boost pulse having a defined shape or profile (with a highcurrent pulse and a background segment) is incorporated as part of theactual welding process so that a plasma boost pulse of a desired shapeis created between the standard pulses of the pulse welding process. Inthis manner, a plasma boost pulse preheats the end of the electrode andcreates a droplet for the next pulse that transfers the droplet to thepuddle. This can be used in a GMAW-pulse welding process usingnon-ferrous metals, such as nickel alloy or titanium alloys. Cored wiresincluding metal cored wire, such as FCAW-G and FCAW-S wires, can be usedwith this welding process. The use of a plasma boost pulse between eachof the high current pulses in the weld process causes a high arc forcepushing the puddle away during melting of the end of the electrodeadvancing toward the workpiece. This gives a hesitation time to allowmelting of the electrode without transferring the molten metal to theworkpiece until the next pulse in the process is created. This aspect ofthe invention can be modified so the sensed voltage of the pulse is usedto adaptively adjust the background portion of the inserted waveform.

The present invention relates to an electric arc welding and method ofusing the same, which performs a pulse welding procedure where a shortarc length (less than about 23 to 25 volts) is desirable to reduce theheat input and to improve fast follow characteristics at increasedtravel speeds. The use of the present invention in cooperation withconventional pulse MIG technology promotes arc stability when operatingat short arc lengths and low voltages. It also ensures reliable,consistent separation of the welding electrode and puddle surface aftera short circuit has been cleared. This procedure enhances rhythm andstability throughout a wide range of operating procedures. The inventionwas developed for high-speed automatic welding of the type performed bya robot where low voltage and, thus, a short arc length is desirable toimprove welding performance at increased travel speeds. However, theinvention is used for sem-automatic applications where reduced heatinput is desirable. Pulse waveforms using this invention can be adjustedfor longer arc lengths and will perform similarly to conventional pulsetechnologies. But, the real advantage is obtained by using low voltagewhere short circuits are more numerous.

This invention improves welding at high travel speeds by improvingstability at low voltages. In accordance with the present invention, ashort circuit is detected and cleared in accordance with standardtechnology; however, after the short circuit is cleared, a plasma boostpulse is created. A plasma boost pulse can be described as pulsing theoutput to a defined amplitude of a defined duration. A plasma boostpulse can be defined as an output current voltage, power or volt/ampereslope level with the preferred implementation using a power level. Thisplasma boost is defined as a power level from 1.0 KW to 20 KW continuingfor 0.2 to 5 ms. In practice, the plasma boost pulse is set for 10 to 15KW with a duration of 0.2 to 0.5 ms. The concept of a plasma boost pulseis an energy based upon a power level maintained for a time. The mannerof obtaining this pulse can be varied. This high current plasma servesto increase the arc force just after the separation of a short circuit.The increase in arc force created by the boost pulse pushes the puddleaway from the electrode, so that another short circuit does not occurduring the same cycle. The plasma boost pulse heats the end of theelectrode to create a molten metal droplet that will become the nextdroplet to be transferred by the subsequent pulse of the pulse weldingprocess. After the short has been cleared and the plasma boost hasincreased the arc force and heated the end of the electrode, the normalpulse weld process is continued. The remaining low background current ofthe pulse welding process allows the droplet to be pushed closer to thepuddle before the next pulse transfers the formed droplet into thepuddle. This invention involves the provision for a current, voltage orpower plasma boost pulse after the short circuit condition has beencleared using a standard short circuit clearing procedure. Thisstabilizes the weld puddle and allows immediate resumption of the normalpulse welding process so that steady operation is possible even at lowvoltages.

The invention is also used for semi-automatic applications wherepenetration must be reduced and is substantially advantageous for metalcored wires where high travel speed is required. It has also beenapplied to pulse welding using flux cored wires. When metal cored wireis used, it has been determined that an effective amount of sulfur inthe core improves the operation of the invention especially when usingmetal cored wire. In practice the sulfur is in the range of 0.010-0.030percent by weight of the wire, and preferably 0.012 to 0.023 percent byweight of the wire.

An advantage of the invention is that parameters of the pulse weldingprocess can be set such as to actually promote shorting events. In suchprocess, the transition to peak is fast to quickly start the formationof a droplet. The pulse peak time is reduced so that the droplet doesnot detach fully from the electrode during the peak current. Thetransfer of arc current to background is fast to quickly reduce the arcforce on the puddle to allow it to rise and advance toward the droplet.The output current is forced below the actual background level tofurther promote the droplet to bridge between the electrode and theworkpiece. The frequency is kept high to keep the droplet size small.When a droplet does bridge from the electrode to the puddle, theshorting response clears the short, and the plasma boost creates thenext droplet on the end of the wire and forces the puddle away from theelectrode.

By a plasma boost pulse between each pulse of the pulse welding processa rhythm is established that has the weld puddle moving to facilitatesmooth pulses with intermediate plasma boost pulses. This allows lowerspatter than obtained in a conventional pulse welding process whereincreased voltages cause lower spatter. The relationship of voltage andspatter by use of the present invention is shifted downwardly from theconventional relationship or operating curve of voltage/spatter. At anyvoltage, spatter is lower using the invention.

Because of the stability of the plasma boost, the process can be run atlevels where every droplet is transferred through a short circuit,thereby significantly reducing the heat input of the welding process.The ability to transfer metal across a short circuit infers that theelectrode, i.e. solid wire, metal cored wire, or flux cored wire, isstable in a short circuit transfer mode. Such as the case with manysteel, stainless, aluminum solid wires, the present invention canimprove the welding performance at shorter arc lengths. Metal coredwires with a stable short arc performance such as Lincoln Electric'sMS-6 ad MC-706 wire can benefit from the present invention. Utilizingthe present invention, these wires have the improved ability to handlepoor fit up conditions and faster travel speeds. These wires include aneffective amount of sulfur to cause the wire to operate uniformly duringshort circuit transfer of metal.

The invention is a refined pulse welding process designed specificallyto allow faster speeds than standard pulse waveforms. It improves lowvoltage welding at high speeds, as it stabilizes the process withshortened arc length. With conventional waveforms, the arc length iskept longer to avoid spatter, thus limiting travel speed. In theinvention, the arc length is kept short and tight and spatter is avoidedwith control of the short circuit cycle. Thus, the shorter arc isstabilized with rhythmic short circuit cycles. The treatment of theshort circuit reduces stubbing and spatter.

The primary object of the present invention is the provision of anelectric arc welder, which welder utilizes a plasma boost pulse after ashort circuit has been cleared and before the next adjacent pulse formelting and transferring molten metal to the weld puddle.

Another object of the present invention is the provision of an electricarc welder, as defined above, which welder can be operated at highspeed, with a short arc length and/or with metal cored of flux coredwires. When using metal cored electrodes, the core has an effectiveamount of sulfur to improve the shape of the weld bead at high travelspeeds.

Still a further object of the present invention is the provision of anelectric arc welder, as defined above, which welder is primarily usefulfor automatic welding in a robot and other mechanized welding mechanismsby a high travel speed, low voltage and low spatter.

Yet another object of the present invention is the provision of a methodof pulse welding wherein an inadvertent short is cleared and thenfollowed by a plasma boost pulse having a high power, such as about 1-5KW to 20 KW for a short time such as about 0.1-5.0 ms, preferably lessthan 1.0 ms.

Yet a further object of the invention is the provision of an electricarc welder and method which can operate at low voltage and converts theshort circuits of such a process to an advantageous metal transfertechnique.

Still a further object of the invention is the provision of an electricarc welder for pulse welding and a method for operating said welder,which welder and method provide faster travel speed, shorter cycle time,higher yield per time and increased productivity for automatic pulsewelding, especially with a robot.

Yet a further object of the invention is provision of a welder andmethod, as defined above, which welder and method performs fast weldingon steel, such as plates in the range of 1.5 to 4.0 mm in thickness,without the risk of weld skips, undercuts or high spatter levels. Thewelder and method provide excellent arc stability at lower arc voltage(shorter arc length) with reduced spatter and washed out bead profile tothereby increase travel speed.

These and other objects and advantages will become apparent from thefollowing description taken together with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a combined block diagram and wiring diagram illustrating anelectric arc welder for performing a pulse welding process in accordancewith the prior art;

FIG. 2 is a graph illustrating a voltage curve and current curve of aprior art pulse welding process;

FIG. 3 is a graph illustrating the signals of various locations in theelectric arc welder illustrated in FIG. 1;

FIG. 4 is an enlarged partially cross-sectioned view of an electrodewith a core and an external shielding gas used in the present invention;

FIG. 5 is a view, similar to FIG. 4, illustrating a flux cored electrodewith a self shielding core and useable in the present invention;

FIG. 6 is a view, similar to FIGS. 4 and 5, showing a solid wireelectrode with an external shielding gas as normally used in the priorart electric arc welder of FIG. 1;

FIG. 7 is a graph with a voltage curve and a current curve illustratingthe pulse welding process in accordance with the preferred embodiment ofthe present invention and containing pictorial representations ofelectrode and workpiece at various stages in the welding process;

FIG. 8 is a combined block diagram and wiring diagram showing anelectric arc welder for performing the pulse welding process illustratedin FIG. 7;

FIG. 9 is a graph showing the signals at various locations in theelectric arc welder shown in FIG. 8;

FIG. 10 is a graph containing a voltage curve and current curve of apulse welding process including an addition to the preferred embodimentof the present invention with pictorial representations of variousstages performed by this addition;

FIG. 11 is a combined block diagram and wiring diagram of an electricarc welder for performing the pulse welding process illustrated in FIG.10;

FIG. 12 is a graph showing signals at various locations in the electricarc welder illustrated in FIG. 11;

FIG. 13 is a graph with a voltage curve and current curve of amodification in the pulse welding process illustrated in FIGS. 10-12 mwherein the background is adaptively adjusted;

FIG. 14 is a combined block diagram and wiring diagram of an electricarc welder for performing the adaptive procedure illustrated in FIG. 13;

FIG. 15 is a graph similar to FIG. 13 illustrating the adaptive featureof the welding process;

FIG. 16 is a graph including a voltage curve and a current curve of apulse welding process incorporating a plasma boost and backgroundsegment between each pulse of the pulse welding process;

FIG. 17 is a combined block diagram and wiring diagram showing anelectric arc welder for performing the pulse welding process illustratedin FIG. 16;

FIG. 18 is a graph illustrating signals at various locations in theelectric arc welder of FIG. 17;

FIG. 19 is a combined block diagram and wiring diagram of an electricarc welder for performing the pulse welding process explained in FIGS.20 and 21;

FIG. 20 is a graph showing signals at various locations in the welderillustrated in FIG. 19;

FIG. 21 is an illustration of the waveform using the welder shown inFIG. 19 and the signals of FIG. 20;

FIG. 22 is an illustration of a waveform obtained by using the inventionwith control of the pulse welding process to assure a short circuit;and,

FIG. 23 is a current curve showing a practical waveform when using thewelder as shown in FIGS. 16-18.

PREFERRED EMBODIMENT

Referring now to the drawings, wherein the showings are for the purposeof illustrating a preferred embodiment of the invention only and not forthe purpose of limiting same, FIGS. 1-3 illustrate a prior art electricarc welder A for performing a pulse welding process, as shown in FIG. 2.The prior art is illustrated since the components used in practicing theinvention are essentially the same as standard components in electricarc welder. Although other welder architecture could be used, thepreferred architecture is a welder controlled by waveform technology aspioneered by The Lincoln Electric Company of Cleveland, Ohio. Two ofmany patents relating to waveform technology is described in BlankenshipU.S. Pat. No. 5,278,390 and Fulmer U.S. Pat. No. 6,498,321, incorporatedby reference herein as background information. In this type of welder, awaveform generator produces the profile for the waveforms used in apulse welding process. The power source creates the pulses in accordancewith the shape determined from the waveform generator by using aplurality of current pulses and at high frequency such as over 18 kHZ.This type of technology produces precise pulse shapes for any desiredwelding process. Even though the invention will be described withrespect to the use of a welder employing waveform technology, theinvention is broader and may be used in other welders, such as SCRcontrolled welders and chopper based welders.

Electric arc welder A shown in FIG. 1 is used to perform a standardpulse welding process as illustrated by the curves in FIG. 2 with aplurality of operating signals indicated at various locations in FIG. 1and by corresponding numbers in FIG. 3. Before addressing the preferredembodiment of the invention, background of the invention as it relatesto the prior art shown in FIGS. 1-3 will be considered. Electric arcwelder A has a power source 10 in the form of a high speed switchinginverter with output leads 12, 14 for creating the pulse welding processbetween electrode E and workpiece W. Power source 10 is driven by anappropriate power supply 16, illustrated as a three phase input. Theprofile of the pulses and separating background current constituting thepulse welding process is determined by a signal on wave shape input 18,in accordance with standard technology. Current shunt 22 communicatesthe arc current of the welding process by lines 24 to a current sensor26 having an analog output 28 used for a feedback control loop. In alike manner, leads 30, 32 communicate the arc voltage to voltage sensor34 having a detect output 36 and a level or amplitude output 38. Thedetect output indicates when the level of voltage plunges during a shortcircuit between electrode E and workpiece W. Level output 38 has asignal representative of the arc voltage across the electrode andworkpiece. Voltage detect output 36 is directed to a shorting responsecircuit 40 having an output 42 which outputs a signal 3, as shown inFIG. 3. When there is a short circuit, there is a detect signal in line42 in accordance with standard technology. Waveform generator 50 isloaded with the particular waveform to perform the welding process. Thiswaveform is indicated as signal 2, shown in FIG. 3. Timer 52 directs atiming signal by lines 54 to waveform generator for the purpose ofinitiating the individual pulses constituting the welding process.Generator 50 also has feedback signals from lines 28, 38 to control thevoltage and current in accordance with the set profile of the waveformgenerator and the existing profile between the electrode and workpiece.The waveform that is to be outputted by power source 10 is signal 2 inline 56. This signal is connected to the input of summing junction oradder 60 having an output 62 for signal 4. This signal, in the prior artwelder A, is the actual signal directed to input 18 of power source 10.The welding process performed by welder A is illustrated in FIG. 2wherein current curve 100 has a series of spaced current pulses 102separated by background current portion 104. Voltage curve 120 is thevoltage between lines 30, 32 and constitutes the arc voltage correlatedwith the arc current of curve 100. The peak voltage is a result ofapplying peak current 102. A low average voltage of curve 120 is due toa high instantaneous arc voltage average with a shorting or below about6.0 volts. When there is a short circuit, arc voltage 120 plunges asindicated by point 122. This voltage plunge indicates a short circuit ofmolten metal between the electrode and workpiece. When that occurs, aclearing procedure overrides the waveform shape in line 56. Upondetection of a short circuit at point 122, a high current is appliedbetween the electrode and workpiece along ramp 106 shown in FIG. 2. Inpractice, this ramp is steep and then become gradual as indicated byportion 108. When the short circuit is cleared by the increased current,in accordance with standard technology, the voltage of curve 120immediately shifts back to a plasma or arc condition. This causes a tailout or recovery of the current along line 110. Consequently, when thereis a short circuit, arc current is increased along ramp 106 and ramp 108until the short is cleared, as indicated by an increased voltage. Thisremoval of the short circuit, stops the output of shortening responsecircuit 40. The operation of welder A is disclosed by the signals 2, 3,4, 7 and 9 as shown in FIG. 3. Signal 7 is the sensed voltage in line36. Under normal circumstances, voltage 120 includes a plurality ofspaced pulses 130 having shapes determined by waveform generator 50 andspacing determined by timer 52. When there is a short at point 122, thevoltage plunges along line 132. This causes a pulse 140 that generatesan output in line 42 which output is in the form of signal 142 generallymatching ramp 106 for the current curve 100 that is added to signal 2.The output of waveform generator 50 is signal 2 constituting thewaveform signal 150 shown in FIG. 3. The output of summing junction 60in line 62 is the summation of signals 2 and 3 which is shown as signal4 in line 62. Ramp 142 is added to waveform 150 so that the outputbetween electrode E and workpiece W is the signal in line 18 controllingthe inverter type power source 10. This is a representation of astandard prior art welder which is modified by the present invention toprovide rapid movement of the electrode with a reduced arc length andreduced spatter.

By using the present invention, the pulse welding process can be shiftedfrom a high voltage process with an arc voltage, in a range greater than26-27 volts, to a low voltage process where the arc voltage is less than25 volts and specifically in the general range of 17-22 volts. With thislow voltage made possible by using the present invention, the arc isstable with a very short arc length below about 0.20-0.30. At about 22volts and 200 amperes the arc length is about 0.15 inches steel wirewith 90% argon and 10% CO₂ This allows a faster travel rate while stillmaintaining a good bead profile. Other wires can be used, such asaluminum or stainless steel. Three different electrodes used in theinvention are illustrated in FIGS. 4-5. In FIG. 4, cored electrode 200is advanced in the direction of the arrow and includes an outer steelsheath 202 and an inner core 204 formed from alloy agents and othercompounds necessary for providing the desired weld metal in the weldbead. As an arc or plasma AC is created between the electrode andworkpiece W, shielding gas 206 is directed around the arc to protect thearc from atmospheric contaminants. The arc length x is a length lessthan 0.30 inches and is created by voltage in the general range of 17-22volts. This type of electrode is well suited for use in the presentinvention. Another cored electrode is shown in FIG. 5, where electrode210 has an outer sheath 212 and an inner core 214. This electrode is aself-shielding electrode where the composition of core 214 providesfluxing agents and other compositions to protect the molten metal as itis transferred through the arc and onto the workpiece W. Again, thiscored electrode is useful in practicing the invention wherein coredelectrodes in the past have not been successfully employed for pulsewelding. FIG. 6 shows solid wire electrode 220 with shielding gas 222.This is the normal wire heretofore used in pulse welding. This typeelectrode is the electrode normally used in MIG welding and particularlyin pulse welding. By using the present invention, electrodes 200, 210and 220 can now be used in pulse welding. Thus, the invention takesadvantage of metallurgical and physical attributes of cored electrodesin pulse welding. The advantages of a cored electrode for STT welding isdiscussed in Stava U.S. Pat. No. 6,071,810 incorporated by referenceherein as background information. Cored electrodes can be used becausethe invention provides low voltage so the voltage range for the weldingprocess by cored electrodes is extended. When using solid wire asillustrated in FIG. 6, the low voltage of the invention allows the wireto travel faster. By using the present invention, all of the electrodesshown in FIGS. 4-6 can be used according to the demands of the weldingprocess. In the past high arc voltages prevented effective uses of alltypes of electrodes. Since the present invention allows very low arcvoltage, the arc length is small and the molten metal often transfers tothe workpiece by a short circuit. This process makes use of coredelectrodes, especially metal cored electrodes, very acceptable for pulsewelding. Indeed, a metal cored electrode with about 0.010 to 0.030sulfur in the core have been proven extremely effective when obtainingthe general advantage of the plasma boost pulse concept of the presentinvention. Wire electrodes, Metal Shield MC6 and MC 706 sold by TheLincoln Electric Company of Cleveland, Ohio have proven to beadvantageous for use with a method using a plasma boost pulse where theshielding gas 75-95% argon with the balance CO₂ gas. These wires conformto the E70C-6M designation. Other metal cored electrodes and selfshielding cored electrodes have taken advantage of the low voltage, lowarc length obtainable in a process performed in accordance with thepresent invention.

The preferred embodiment of the invention is illustrated in FIGS. 7-9that produces the pulse welding method best shown in FIG. 7. Currentcurve 300 includes spaced pulses 302 separated by background portions304 determined by the output of waveform generator 50 with the pulsesspaced by the output of timer 52. Of course, timing can be built intothe program of the waveform generator. Background current 304 isprovided between pulses 302 for use in keeping the arc lit after moltenmetal M has been formed and deposited onto the workpiece in the moltenmetal weld puddle. Voltage curve 310 includes a short circuit detectpoint 312 and a short circuit clear point 314. Curve 300 shows thenormal high current clearing routine to generate portions 306, 308corresponding to portions 106 and 108, respectively, of the prior artshown in FIG. 2. The invention involves the provision of a plasma boostpulse 320 preferably after the short circuit clear point 314 so theboost pulse occurs during an arc condition or a plasma condition. Inpractice, this plasma pulse is created during an interrupt of the outputfrom waveform generator 50 and is substituted for the output of thegenerator at input 18 of power source 10. Plasma boost pulse 320 is aregulated power in the general range of 5-20 KW and preferably less thanabout 10-15 KW. For aluminum, the power may be as low as 1.0 KW. Thispulse has a peak portion 322 that has a time distance y which isgenerally less than 5.0 ms and preferably in the range of 0.2-5.0 ms. Inthe present implementation, the time is 0.3 ms. Pulse 320 is terminatedat the end of the peak portion 322 to enter a current reduction sectionwhere the arc current falls to background current level 304. In thepreferred embodiment, this reduction in current is a long trailing edge324 and a generally gradual tail out portion 326 so the plasma boostpulse is terminated before 5.0 ms. The operation of the plasma boost isdepicted in the pictorial representations I-VI at the top of FIG. 7.Electrode E advances toward workpiece W while molten metal M is formingas shown at position I. The current between the electrode and workpieceis then increased to peak of pulse 302 causing the end of electrode E tomelt further and produce a molten metal ball M. The operation of peak302 is at position II. Workpiece W involves a molten metal puddle Pwhich is cavitated by the arc force between electrode E and workpiece W.After position II, in normal pulse welding, the molten metal M at theend of electrode E is transferred through the arc to the puddle P duringthe background portion 304 of the process. Then the process is repeatedas shown in position VI. A short circuit between electrode E and puddleP by molten metal M is not formed as a part of a normal pulse weldingoperation. When a short circuit occurs as shown at position m, the arcvoltage is plunged at point 312. The short circuit then initiates a highcurrent clearing routine or sequence represented by portions 306, 308 toneck off and separate molten metal M from electrode E as shown inposition IV. Then the present invention is implemented. At the clearanceof the short circuit represented by a rapid rise in voltage at point 314a plasma boost pulse is outputted. The plasma boost pulse force puddle Maway from electrode E as shown at position V. This high arc forcecavitates puddle P drastically to assure a separation between moltenmetal M and molten puddle P. This assures that there is no incipientshort or short circuit until after the next pulse 302. After pulse 320shown at position V, the low background current portion 304 isimplemented by waveform generator 50. This allows the puddle P ofworkpiece W to become quiescent so that the cavitation is decreased in amanner illustrated at position VI. By using the present invention asshown in position V, a substantially larger spacing or gap G is providedbetween the end of electrode E and puddle P of workpiece W. This largegap is the result of the plasma boost pulse following the necking andrupture of the short circuit. The present invention allows lowervoltages, faster operation and uniform weld beads with low spatter.Creation of the arc forced gap controls the shape of the molten metal inthe puddle directly under the electrode as the short circuit has beencleared. Position V represents a primary advantage obtained by using aplasma boost pulse following a short circuit in a pulse weldingoperation. It is possible to use only plasma boost pulse to both clear ashort circuit, as well as force the puddle into a large arc forcecavitation shown in position V. However, this can increase spatter. Soclearing of the short circuit is preferred. Since the short circuit iscleared and followed by a high power plasma boost pulse, the shortcircuit event is no longer disruptive of the pulse welding process. Aswill be shown later, the existence of periodic short circuits may bebeneficial and are surely rendered less detrimental.

The pulse welding process with a plasma boost pulse is performed byelectric arc welder B shown in FIG. 8. The same functional components asused in welder A, shown in FIG. 1, with the same number and same signalsare used in welder B. To practice the invention, welder B is providedwith a plasma boost profile circuit 350 having a start interrupt signalin line 352 with the short circuit is cleared at point 314 in FIG. 7. Asignal in line 352 when the point 314 is reached is communicated totimer 360 by line 362. This starts timer to create an interrupt time.This interrupt signal in line 362 continues until timer proceeds to itsset time. The signal in line 362 from timer 360 sets the duration of theinterrupt during which the plasma boost profile circuit 350 is operated.Output 354 processes the boost pulse profile during the interrupt whenthe interrupt signal in line 364 shifts switch 370 from the normalcontact 372 and the interrupt contact 374. When timer 360 holds switch370 in the interrupt position at 5 contact 374 plasma boost circuit 350outputs a profile signal in line 354 so long as timer 360 is timing togive a signal in line 364. This profile is the plasma boost pulse 320shown in FIG. 7. Of course, switch 370 is a digital software switch toshift from the output 62 of summing junction 60 to the interruptposition while circuit 350 processes a profile indicated as signal 5.This signal is directed to input 18 of power source 10. The varioussignals are shown in FIG. 9 with the numbers corresponding to thesignals in FIG. 3. The new signals 5, 6, 10 and 11 are shown in thelower portion of FIG. 9 and are coordinated in time with the othersignals previously described. When the short circuit has been cleared,shorting response circuit 40 creates signal 10 in line 352, which signalis a pulse 380. This pulse starts the timing signal 11 which is a rampsignal 382 having a time out position 384. As long as timer 360 istiming, an interrupt signal 390 is maintained while the plasma boostprofile in line 354 is processed by power source 10. During theinterrupt and signal output indicated by pulse 390, the control voltageon input line 18 is in the form of pulse 392 shown as signal 6. Inpractice, it is beneficial when the short circuit is formed (point-312of FIG. 7) at a low current which will minimize any spatter created.Since the cross section of the short circuit is minimal, only a minimalincrease in current by the shorting ramp is required to clear the shortcircuit. The short clears at a relatively low current resulting inminimal spatter created by the release of the short.

By using the present invention as shown in FIGS. 7-9, a plasma boost isprovided after the normal short circuit clearing routine has beenperformed by shorting response circuit 40 in accordance with standardpractice. In accordance with a broad aspect of the invention, the plasmaboost pulse can replace the short clearing routine; however, this is nota preferred implementation of the present invention. The standard pulseprogram from waveform generator 60 can be modified to improve theshorting events and improve the response to the short circuits so theevents are not disruptive. These modifications include a fast transitionfrom the low background current to the high peak current at the leadingedge of pulse 302. This quickly increases the output to a level abovethe transition current to start melting of a droplet on the end of theelectrode. Then, a fast transition from the high peak current of pulse302 to the low background current 304 can be provided. This quicklyreduces the arc force between the droplet and the puddle. As this arcforce is removed, the puddle and droplet can short easily. Thetransition from the peak current to the background current 302 willshort more often and positively if the initial transition overshoots thebackground current slightly. Thus, the trailing edge of pulse 302transitions to a current slightly below the background current 304. Thisaspect of the invention is disclosed in more detail later whendiscussing FIG. 22. As illustrated in FIG. 7, the shorting response is amulti-ramp response that minimizes the initial response to the shortcircuit for separating incipient shorts and then increases the currentresponse for clearing harder shorting events. This method has been usedfor many years in the Power Wave 455 manufactured by The LincolnElectric Company when processing standard CV programs.

An addition can be made to the preferred embodiment of the presentinvention as illustrated in FIGS. 10-12 wherein the plasma boost pulseor routine is modified to promote consistent detachment of the moltenmetal. The plasma boost creates a molten droplet on the end of theelectrode that will be transferred during the next pulse cycle. Once theplasma boost pulse is completed, the standard pulse waveforms areresumed. However, a short circuit will not occur at the same time foreach of the pulses in the pulse welding process. Furthermore, the timerequired to clear a short is inconsistent from one short to the next.Consequently, the time the short clears in relationship to the nextpulse determined by timer 52 will not be consistent. The remaining timeafter the plasma boost pulse is completed will be different whenutilizing the preferred embodiment of the present invention. It ispresumed that the background current 304 has sufficient time in thewaveform created by waveform generator 50 to allow the electrode totravel closer to the puddle before the molten metal is transferred. Thistime is inconsistent from one short to the next for the reasons stated.Consequently, the position at the end of the electrode with respect tothe puddle will not be consistent. A method for improving thisconsistency allows the end of the electrode to travel a consistentdistance before the next pulse. This improvement in the basic method ofthe invention uses a dedicated background time and amplitude routineafter the plasma boost itself has been processed. The waveform creatingthe plasma boost pulse is modified to include its own background currentportion after the pulse. Consequently, timer 360 is used to control theduration of the plasma boost pulse and the background current time andmagnitude. The plasma boost pulse serves to build a consistent dropleton the end of the electrode at a consistent distance from the puddle asshown in the top pictorial representations of FIG. 10. In order tomaintain this consistent operation before the next pulse, a consistenttime and amplitude for the background segment or portion is used in themodification of the preferred embodiment. This modification is shown inFIGS. 10-12. The plasma boost pulse is expanded to include a dedicatedbackground amplitude and time. Timer 360 is used to set the timestarting with the short circuit clearance signal appearing on line 352.In accordance with this modification of the present invention, electricarc welder C shown in FIG. 11 is modified to reset timer 52 at the endof the interrupt during which line 354 controls input 18. The resetsignal is a signal on line 400. During the interrupt, plasma boostcircuit 350 creates a signal 5 to generate a waveform 410 having aplasma boost pulse portion 412 and a background current portion 414terminating at time 416. This is the time out of timer 360 to create areset signal in line 400. When timer 360 starts its timing sequence,there is an interrupt shown as pulse 420 in FIG. 12. This is the sameinterrupt as previously described. Timer 52 times along line 422 asshown in FIG. 12. At position 424, timer 52 resets causing a signal attime 426 in line 54 to start the next pulse 150 in signal 2 of generator50. In accordance with this embodiment of the invention, welder Ccreates a reset signal in line 400 when timer 360 reaches its set timeat the end of the tailout section 414 at the plasma boost waveform 410.This reset signal is at time 430 shown in FIG. 12. Reset signal 1terminates pulse 150 of signal 2 at the end of the plasma boost portionof waveform 410 to create a partial pulse 150 a shown in FIG. 12. Thisthen initiates the next pulse 150 b of signal 4 shown in FIG. 12. Duringinterrupt 420, a waveform 410 is created by circuit 350 on line 354.This waveform during the interrupt has a precise profile for the plasmaboost pulse 412 and the background current portion or segment 414.Immediately after that background current portion has been implementedby power source 10, the next pulse 150 b is caused to proceed.Consequently, when there is a short circuit there is a precise pulse andtail out or background current amplitude and time. This is shown in FIG.10. The signal on line 18 by the interrupt position of switch 370 is awaveform 410 with pulse portion 412 and background current portion 414.A signal in line 400 occurs at time 416. This is when the predeterminedwaveform of the interrupt has been completed. Consequently, elements412, 414 and 416 are consistent with each short. Thereafter, a new pulse302 is initiated by timer 52. A signal 6 shown in FIG. 12 is applied toinput 18 for controlling the profile of the current or power betweenelectrode E and workpiece W. The new profile is profile 440 in FIG. 12.Consequently, the output of waveform generator 50 is interrupted at theend of the short and a given pulse and background current segment isprocessed. The result of this waveform is shown in positions I-III inFIG. 10. Upon creation of portion 412, the arc force pushes puddle P soit moves away from the end of electrode E. This is shown at position I.Thereafter, the background current portion allows puddle P to reform ina uniform manner. This is shown at position II. At the end of theprofiled waveform 410, the molten metal M is ready to be transferred toworkpiece W as shown at position III. This creates a consistentoperation after each short circuit. Such modification of the preferredembodiment improves the quality of the weld while still maintaining theadvantages of using a plasma boost pulse at the end of the shortcircuit. Consequently, the plasma boost signal includes a dedicatedbackground portion 304 with a selected amplitude and duration, which isat a different level than level 414 in FIG. 10. The interrupt signal ismaintained through waveform 410 including plasma boost pulse 412 anddedicated background portion or segment 414. Timer 52 is reset at theend of a dedicated background time. During the dedicated backgroundportion, the waveform generator is ignored because the interrupt hasswitched control of input 18 to the output of plasma boost controlcircuit 350. The waveform generator is reset by timer 52.

A slight modification of the embodiment illustrated in FIGS. 10-12 isdisclosed in FIGS. 13-15. Molten metal M formed on the end of theelectrode after the plasma boost pulse will vary according to certainconditions during the plasma boost pulse. Consequently, a feedback loopsensing the arc voltage during the plasma boost pulse can be used toadjust the dedicated background segment 414. The arc voltage during theplasma boost pulse indicates the arc length during the pulse. This arclength is used to calculate background current portion amplitude and/orduration. Since the plasma boost is defined as a function of power, thevoltage feedback is used to calculate the relative arc length and modifythe background amplitude and/or duration. Adapting the backgroundamplitude and duration will promote even more consistency of theelectrode placement with regard to the puddle after a short circuit. Anindependent adaptive control is used in welder D shown in FIG. 14. Thisadaptive loop modifies background portion 414 in accordance with thesensed arc voltage occurring during the pulse portion 412 of waveform410. The gain of this second adaptive control loop must be set so thatthe short plasma boost will directly affect the next background currentsegment. Consequently, only the background current amplitude andduration for the interrupt being processed is adapted. Thus, electricarc welder D allows the plasma boost to be controlled by an arc voltagefeedback loop. To this end, adjustment of the amplitude and duration ofthe background portion 414 is accomplished by circuit 500 having aninput 502 representing the arc voltage from voltage sensor 34. Output504 is communicated with the plasma boost circuit to adjust thebackground portion during the interrupt determined by the time switch370 is in the interrupt position 374. This 5 novel concept is bestillustrated by a comparison of FIG. 13 and FIG. 15. In FIG. 13, thebackground portion 414 (normally current) is a fixed profile, aspreviously described. Voltage from line 502 in FIG. 14 adjusts portion414 into the dashed line configuration of FIG. 15 where the newbackground portion 414 a of waveform 410 terminates at a new point 416a. Portion 414 a is adjusted by the arc voltage during pulse portion412, which voltage essentially corresponds to the arc length during theplasma boost pulse portion of waveform 410. Otherwise, electric arcwelder D shown in FIG. 14 is the same as welders A, B and C, aspreviously described.

Another use of the plasma boost pulse is described in FIGS. 16-18.Plasma boost pulse 600 with a boost pulse portion 602 and backgroundportion 604 is inserted between each pulse 302 of curves 100, 120 asshown in FIG. 16. In this manner, the plasma boost pulse preheats theend of the electrode and creates a droplet for the next pulse 302 fortransfer to the molten metal puddle P. The first segment of the plasmaboost pulse is a pulse that will preheat the end of the electrode andcreate a droplet. This preheat has been advantageously used inGMAW-pulse welding using non-ferrous metals, such as nickel alloys andtitanium. In this process of a boost pulse between each standard pulse,metal cored wires and flux cored wires, as shown in FIGS. 4 and 5, havebeen used to provide FCAW-G and FCAW-S welding processes. The process isimplemented by electric arc welder F which differs from welder C shownin FIG. 11 by removing the shorting response circuit 40 and providing atwo way reset line 608. The output of plasma boost profile circuit 350is the fixed waveform 410 directed to input 18 when switch 370 isshifted to the interrupt position 374 by the logic on line 364. Thisline is signal 11 shown in FIG. 18 where timer 360 times along portion610 until it reaches its set count at point 612. Interrupt pulse 620 isin existence when switch 370 is held in the interrupt position 374. Theinterrupt is started at time 612 when timer 360 starts. When the timerstarts at time 612, the output on line 354 is a waveform with profile600 a shown in FIG. 18. Timer 52 starts the next pulse 150 at time 424and terminates interrupt 620 at this time. Thus, during interrupt 620waveform 600 a is directed through line 354 to input 18. Thus, signal 6alternates between signal 2 from waveform generator 50 and fixed pulseprofile shape 600 b corresponding to waveform 410 in line 354. Duringthe time between timer resets, the interrupt is being processed to drivepower source by input 18 from circuit 350. Thus, a plasma boost pulse600 is routinely implemented between the normal pulse 302 by powersource 10. The operation of this use of the power boost pulse is bestillustrated at the upper portion of FIG. 16 where electrode E is meltedso that molten metal M is transferred to workpiece W between positions Iand II. Then, in accordance with standard pulse welding technology,molten metal M is transferred to puddle P of workpiece W as shown inposition HI. At position IV waveform 600 including a high power plasmaboost is implemented between electrode E and workpiece W. This waveformcauses action of puddle P shown in position IV. When the fixedbackground portion 604 of plasma boost pulse waveform 600 a is appliedthrough the arc, puddle P recedes toward the molten metal M and awaitsthe next transfer pulse 302. This is shown at position V. the pulseportion of waveform 600 a will heat the end of the electrode and createa molten droplet that is transferred during the next pulse. This methodcan be used alone or in combination with the timing sequence shown inFIG. 18. Other arrangements can be used to insert a plasma boost pulsebetween the standard current pulses 302 from waveform generator 50.Welder F could have the background adjustment feature of welder D asshown in FIG. 14 as an option. Preferably, the tailout for waveform 600a is fixed. Adaptive feedback from the voltage or arc length isoptional.

FIG. 23 is a current curve of the practical implementation of the novelprocess where a plasma boost pulse is created between each pulse of astandard pulse welding process. A short circuit at point 910 occursafter each pulse 900. This short circuit is not at the peak of pulse900, but is after decay portion 902. The short is cleared naturally bythe rhythmic movement of the puddle to create a current hump 904. Thereis a delay before the short circuit clearance routine increases thecurrent as so far explained. If the short circuit is cleared naturallybefore the delay expires, there is no clearing current increase. Thus,the short is often cleared at point 912 before there is a rush of shortclearing current. This second signal at point 912 is the trailing edgeof pulse 140 in signal 9 as shown in FIG. 9. When the second signal iscreated from voltage sensing device 34, the short is cleared and plasmaboost pulse 930 is created. Because of inherent time delays in thecircuitry, there is a slight time delay 920 between the second signal atpoint 912 and start of pulse 930. Thereafter, background current 932continues to the next pulse. The slight delay before clearing currentwould be before creation of pulse 142 in FIG. 9, but during the shortthe delay may be greater than the time to clear the short naturally. Ifthe short is cleared before the delay has expired, then the welder goesdirectly into the plasma boost with its inherent delay 920. During pulse900, there is a sudden increase in current to increase the arc energy toform and squeeze a molten droplet extending from the end of theelectrode. During time R, the pulse is ramped down to relax the plasmaforce depressing the molten puddle. This allows the puddle to risetoward the droplet. When there is a short at point 910, the droplet hascontacted the puddle. As soon as the short terminates at point 912, agentle plasma boost pulse pushes the puddle away and conditions theelectrode tip. This assures reliable separation of the metal from thetip and the puddle resulting in a stable rhythm of the cycles. The delaybefore the clearing current allows the short to clear by the rhythm andnot by a clearing current. If it does not clear during the delay, thenthe standard current clearing routine is implemented. The second signalat point 912 informs the controller that the short has been clearedwhether naturally or by a clearing current. Then the plasma boost pulseis outputted. This is the practical operation of the welder in FIGS.16-18.

The use of a waveform including a plasma boost pulse portion with adifferent short circuit clearing routine is another aspect of thepresent invention and is shown in FIGS. 19-21. Welder G is similar towelder C disclosed in FIG. 11 with the addition of a standardpremonition circuit 700 with an input 702 and an output 704. A logic onthe output indicates when the dv/dt of the arc voltage from sensor 34exceeds a given level indicating an impeding short circuit during theclearance routine for a short circuit. The dv/dt circuit is standard anddetects a slope equal to or greater than a reference value signaling theshort is about to break. This circuit stops the shorting responsecircuit 40 so that the signal in line 325 terminates the arc portion 712of waveform 710 shown in FIG. 21 and initiates the plasma portion 714 onoutput 354 of plasma boost profile circuit 350. The output 704 ofpremonition circuit 700 is shown as pulse 720 in signal 12, one of themany number signals of welder G shown in FIG. 20. The various numberedsignals in FIG. 20 correspond to the numbers used in FIG. 19. Welder Ggenerates the signals shown in FIG. 20, which signals are essentiallythe same as the like numbered signals illustrated in FIG. 11 for welderC. The basic difference between welder G and welder C relates to shortclearing portion 712 of waveform 710. When the short occurs at point 132shown in FIG. 20, waveform portion 712 of waveform 710 is implemented bythe shorting response circuit 40. This portion of the waveform isdifferent and includes a immediate reduction in current at the time ofthe short represented by portion 730. Circuit 40 holds the current lowfor a preset time 732, after which a clearance routine for the shortcircuit is implemented. This routine starts with a rapid increase incurrent along slope portion 734 followed by a second slope portion 736which is somewhat more gradual. As this current increase is directedthrough the short circuit, the short circuit begins to neck causing anincrease in the dv/dt. When this derivative reaches a specific levelpulse 720 is created. This pulse immediately plunges the current to alow level similar to the level at reduction point 730. The premonitionrelation can be dv/dt, di/dt, dp/dt or other derivatives of time.Reduction of current caused by pulse 720 also starts waveform portion714 of general waveform 710 illustrated in FIG. 21. In anotherembodiment, waveform 710 is started by a break in the short circuit.Waveform portion 714 includes the plasma boost pulse 740 having atailout portion 742. This tailout portion is more distinct in FIG. 19,but has a variety of configurations. Welder G utilizes a unique shortcircuit clearing procedure whereby the termination of the clearingroutine is determined by the impending rupture of the short circuit, asopposed to a voltage detector employed in welder C. Otherwise, theclearing procedure is generally the same. The exception is the reducedcurrent portion for time 732. Metal transfer line or current 744 is lessthan the peak current, but greater than the maximum current of theplasma boost pulse. When there is a short, the short circuit is clearedand a plasma boost pulse is initiated to force the molten metal puddlefrom the advancing electrode while the advancing electrode is forming amolten metal ball for the next transfer. By using waveform 710 shown inFIG. 21, transfer of metal by short circuit is not disruptive and mayeven be advantageous. Indeed, it has been found when using the inventionthat transfer by a short circuit process after each pulse 150 of thepulse welding process has some advantages. Consequently, a modificationof the invention has been developed which relies upon transfer of metalby short circuit in a pulse welding process. This modification uses thenovel plasma boost pulse of the invention and is described in FIG. 22.

The use of the novel plasma boost pulse in a pulse welding process forthe purpose of actually transferring metal by short circuit transfer,instead of the normal spray transfer is illustrated in FIG. 22. Thisaspect of the invention uses the elements from various electric arcwelders so far described in detail. A normal pulse welding waveform isillustrated as curve 800 having pulses 802 separated by backgroundcurrent portions 804 and spaced to produce a period n. Each peak currentstage 806 has a length or process time to melt the advancing electrodefor the purposes of spray transfer as is normal. This transfer throughthe arc occurs at the end of the peak current stage and shown as point810. Pulse 802 is intended to have enough energy to melt and propel adroplet of molten metal toward the workpiece. If this action does notoccur, there will be a short circuit created when the molten metal ballon the end of the advancing wire contacts the molten metal of thepuddle. This contact creates a short circuit indicated at point 812 toimplement and bring into operation the method so far described where ashort circuit creates a metal clearance routine and then provides thenovel plasma boost pulse, with or without a controlled secondarybackground current. For the purposes of explaining the differencesbetween a normal pulse welding process and the aspect of the inventionshown in FIG. 22, the parameters of a representative normal pulsewelding process using curve 800 are helpful.

Peak current 806 has a value of 550 amperes and a length of time ofabout 2.0 ms. Background current 804 has a level of 90 amperes whileperiod n is about 8.3 ms. These parameters are representative of a pulsewelding process to which the invention has been added, as previouslydescribed. In FIG. 22 the present invention is used in a process thatutilizes a short circuit condition to transfer the molten metal. Thisprocess can be employed due to the quiet puddle dynamics resulting fromuse of the present invention. The new pulse weld process of FIG. 22 isillustrated by curve 820 where current pulses 830 are provided at afrequency which is increased as much as twice the frequency used incurve 800. With this high frequency, period m between pulses 830, whencompared to a normal pulse welding process, can be reduced to about 4.3ms. The template for the process depicted as curve 820 also has othermodifications from the normal pulse welding curve 800. For instance, thepeak current is reduced to a level, such as 475 amperes, and has ashortened time of 1.5 ms. These are representative parameters, butindicate that pulse 830 is not intended to actually separate the moltenmetal from the electrode and propel it toward the workpiece as done bypulse 802. Consequently, as the wire electrode is advancing toward theworkpiece, pulse 830 merely forms a molten metal ball on the end of thewire. As the peak current is decreased, the molten metal ball on the endof the advancing wire progresses toward the molten metal puddle. Inaccordance with the illustrated embodiment of the invention shown inFIG. 22, the reduction of current after the peak stage 832 is belowbackground current level 834 to a lower current point 840. This reducesthe amount of arc force between the advancing molten metal ball and themolten metal puddle. The puddle, thus, rises toward the ball as the ballis moving toward the molten metal puddle. This causes a short circuit atpoint 842. This short circuit is detected as previously described. Thepresent invention then creates waveform 850. This waveform includes apulse portion 852 and a tailout portion 854. This waveform occurs duringthe plasma portion when there is an arc to initiate melting of theadvancing wire preparatory to the next pulse 830. As previouslydescribed a clearing circuit is activated at point 842 to provide aclearance routine having two slope portions 862, 864. By using theinvention disclosed in FIG. 22 curve 820 provides pulses at a higherfrequency and with less energy in the pulses. A circuit activated at theend of a pulse plunges the arc current to assure a short circuit. Thus,a short circuit metal transfer is effected. The advantage of using thenovel plasma boost waveform following termination of the actual shortcircuit allows the use of this novel pulse welding process.

Several pulse welders and welding methods have been described. Featuresof the various welders and methods can be combined or eliminated inaccordance with the desires of the manufacturer and/or user. It isexpected that certain modifications from one embodiment will be used inother embodiments that do not present technical inconsistencies.

1. An electric arc welder for performing a pulse welding process by avoltage driven current between an advancing electrode and a workpiece,said welder having an output voltage and comprising: a short detectingcircuit creating a short signal upon occurrence of a short circuitbetween said advancing electrode and said workpiece and a boost circuitto create a plasma boost pulse after creation of said short signal. 2.An electric arc welder as defined in claim 1 including a circuit toincrease said current after said signal and before said plasma boostpulse.
 3. An electric arc welder as defined in claim 2 wherein saidplasma boost pulse has a regulated power of 5-20 KW.
 4. An electric arcwelder as defined in claim 3 wherein said plasma boost pulse has aduration of 0.2-5.0 ms.
 5. An electric arc welder as defined in claim 1wherein said plasma boost pulse has a regulated power of 5-20 KW.
 6. Anelectric arc welder as defined in claim 5 wherein said plasma boostpulse has a duration of 0.2-5.0 ms.
 7. An electric arc welder as definedin claim 2 wherein said plasma boost pulse has a duration of 0.2-5.0 ms.8. An electric arc welder as defined in claim 1 wherein said plasmaboost pulse has a duration of 0.2-5.0 ms.
 9. An electric arc welder asdefined in claim 8 wherein said electrode is a cored wire.
 10. Anelectric arc welder as defined in claim 7 wherein said electrode is acored wire.
 11. An electric arc welder as defined in claim 5 whereinsaid electrode is a cored wire.
 12. An electric arc welder as defined inclaim 3 wherein said electrode is a cored wire.
 13. An electric arcwelder as defined in claim 2 wherein said electrode is a cored wire. 14.An electric arc welder as defined in claim 1 wherein said electrode is acored wire.
 15. An electric arc welder as defined in claim 2 whereinsaid plasma boost pulse is by regulation of arc current.
 16. An electricarc welder as defined in claim 2 wherein said plasma boost pulse is byregulation of arc voltage.
 17. An electric arc welder as defined inclaim 2 wherein said plasma boost pulse is by regulation of arc power.18. An electric arc welder as defined in claim 2 wherein said plasmaboost pulse is regulated by a slope output characteristic.
 19. Anelectric arc welder as defined in claim 1 wherein said plasma boostpulse is by regulation of arc current.
 20. An electric arc welder asdefined in claim 1 wherein said plasma boost pulse is by regulation ofarc voltage.
 21. An electric arc welder as defined in claim 1 whereinsaid plasma boost pulse is by regulation of arc power.
 22. An electricarc welder as defined in claim 1 wherein said plasma boost pulse isregulated by a slope output characteristic.
 23. An electric arc welderas defined in claim 14 including a timer to set the period of saidpulses of said pulse welding process.
 24. An electric arc welder asdefined in claim 8 including a timer to set the period of said pulses ofsaid pulse welding process.
 25. An electric arc welder as defined inclaim 5 including a timer to set the period of said pulses of said pulsewelding process.
 26. An electric arc welder as defined in claim 2including a timer to set the period of said pulses of said pulse weldingprocess.
 27. An electric arc welder as defined in claim 1 including atimer to set the period of said pulses of said pulse welding process.28. An electric arc welder as defined in claim 17 wherein said boostcircuit creates a controlled, background segment following said plasmaboost pulse.
 29. An electric arc welder as defined in claim 28 includinga timer to set the period of said pulse of said pulse welding processand a circuit responsive to the end of the background segment to resetsaid timer.
 30. An electric arc welder as defined in claim 16 whereinsaid boost circuit creates a controlled, background current segmentfollowing said plasma boost pulse.
 31. An electric arc welder as definedin claim 3 including a timer to set the period of said pulse of saidpulse welding process and a circuit responsive to the end of thebackground segment to reset said timer.
 32. An electric arc welder asdefined in claim 15 wherein said boost circuit creates a controlled,background current segment following said plasma boost pulse.
 33. Anelectric arc welder as defined in claim 32 including a timer to set theperiod of said pulse of said pulse welding process and a circuitresponsive to the end of the background segment to reset said timer. 34.An electric arc welder as defined in claim 14 wherein said boost circuitcreates a controlled, background current segment following said plasmaboost pulse.
 35. An electric arc welder as defined in claim 34 includinga timer to set the period of said pulse of said pulse welding processand a circuit responsive to the end of the background segment to resetsaid timer.
 36. An electric arc welder as defined in claim 13 whereinsaid boost circuit creates a controlled, background current segmentfollowing said plasma boost pulse.
 37. An electric arc welder as definedin claim 36 including a timer to set the period of said pulse of saidpulse welding process and a circuit responsive to the end of thebackground segment to reset said timer.
 38. An electric arc welder asdefmed in claim 8 wherein said boost circuit creates a controlled,background current segment following said plasma boost pulse.
 39. Anelectric arc welder as defined in claim 38 including a timer to set theperiod of said pulse of said pulse welding process and a circuitresponsive to the end of the background segment to reset said timer. 40.An electric arc welder as defined in claim 7 wherein said boost circuitcreates a controlled, background current segment following said plasmaboost pulse.
 41. An electric arc welder as defined in claim 40 includinga timer to set the period of said pulse of said pulse welding processand a circuit responsive to the end of the background segment to resetsaid timer.
 42. An electric arc welder as defined in claim 5 whereinsaid boost circuit creates a controlled, background current segmentfollowing said plasma boost pulse.
 43. An electric arc welder as definedin claim 42 including a timer to set the period of said pulse of saidpulse welding process and a circuit responsive to the end of thebackground segment to reset said timer.
 44. An electric arc welder asdefined in claim 2 wherein said boost circuit creates a controlled,background current segment following said plasma boost pulse.
 45. Anelectric arc welder as defined in claim 44 including a timer to set theperiod of said pulse of said pulse welding process and a circuitresponsive to the end of the background segment to reset said timer. 46.An electric arc welder as defined in claim 1 wherein said boost circuitcreates a controlled, background current segment following said plasmaboost pulse.
 47. An electric arc welder as defined in claim 46 includinga timer to set the period of said pulse of said pulse welding processand a circuit responsive to the end of the background segment to resetsaid timer.
 48. An electric arc welder as defined in claim 46 includinga circuit to sense said arc voltage during said plasma boost pulse and acircuit to adjust said background segment based upon said sensed arcvoltage.
 49. An electric arc welder as defined in claim 44 including acircuit to sense said arc voltage during said plasma boost pulse and acircuit to adjust said background segment based upon said sensed arcvoltage.
 50. An electric arc welder as defined in claim 42 including acircuit to sense said arc voltage during said plasma boost pulse and acircuit to adjust said background segment based upon said sensed arcvoltage.
 51. An electric arc welder as defined in claim 40 including acircuit to sense said arc voltage during said plasma boost pulse and acircuit to adjust said background segment based upon said sensed arcvoltage.
 52. An electric arc welder as defined in claim 38 including acircuit to sense said arc voltage during said plasma boost pulse and acircuit to adjust said background segment based upon said sensed arcvoltage.
 53. An electric arc welder as defined in claim 36 including acircuit to sense said arc voltage during said plasma boost pulse and acircuit to adjust said background segment based upon said sensed arcvoltage.
 54. An electric arc welder as defined in claim 34 including acircuit to sense said arc voltage during said plasma boost pulse and acircuit to adjust said background segment based upon said sensed arcvoltage.
 55. An electric arc welder as defined in claim 32 including acircuit to sense said arc voltage during said plasma boost pulse and acircuit to adjust said background segment based upon said sensed arcvoltage.
 56. An electric arc welder as defined in claim 30 including acircuit to sense said arc voltage during said plasma boost pulse and acircuit to adjust said background segment based upon said sensed arcvoltage.
 57. An electric arc welder as defined in claim 28 including acircuit to sense said arc voltage during said plasma boost pulse and acircuit to adjust said background segment based upon said sensed arcvoltage.
 58. An electric arc welder as defined in claim 14 wherein saidvoltage is less than 25 volts.
 59. An electric arc welder as defined inclaim 14 wherein the arc length is less than 0.30 inches.
 60. Anelectric arc welder as defined in claim 13 wherein said voltage is lessthan 25 volts.
 61. An electric arc welder as defined in claim 13 whereinthe arc length is less than 0.30 inches.
 62. An electric arc welder asdefined in claim 12 wherein said voltage is less than 25 volts.
 63. Anelectric arc welder as defined in claim 12 wherein the arc length isless than 0.30 inches.
 64. An electric arc welder as defined in claim 11wherein said voltage is less than 25 volts.
 65. An electric arc welderas defmed in claim 11 wherein the arc length is less than 0.30 inches.66. An electric arc welder as defined in claim 10 wherein said voltageis less than 25 volts.
 67. An electric arc welder as defined in claim 10wherein the arc length is less than 0.30 inches.
 68. An electric arcwelder as defined in claim 9 wherein said voltage is less than 25 volts.69. An electric arc welder as defined in claim 9 wherein the arc lengthis less than 0.30 inches.
 70. An electric arc welder as defined in claim5 wherein said voltage is less than 25 volts.
 71. An electric arc welderas defined in claim 5 wherein the arc length is less than 0.30 inches.72. An electric arc welder as defined in claim 3 wherein said voltage isless than 25 volts.
 73. An electric arc welder as defined in claim 3wherein the arc length is less than 0.30 inches.
 74. An electric arcwelder as defined in claim 2 wherein said voltage is less than 25 volts.75. An electric arc welder as defined in claim 2 wherein the arc lengthis less than 0.30 inches.
 76. An electric arc welder as defined in claim1 wherein said voltage is less than 25 volts.
 77. An electric arc welderas defined in claim 1 wherein the arc length is less than 0.30 inches.78. An electric arc welder as defined in claim 76 wherein said pulsewelding process includes a succession of waveforms and said waveformsare created by a series of short current pulses generated at a frequencygreater than 18 kHz and with a profile controlled by a waveformgenerator.
 79. An electric arc welder as defined in claim 78 includingan interrupt circuit to interrupt said waveform upon occurrence of ashort circuit between said electrode and said workpiece.
 80. An electricarc welder as defined in claim 79 wherein a waveform profile of a plasmaboost pulse is processed by said welder during said interrupt.
 81. Anelectric arc welder as defined in claim 14 wherein said cored wire is ametal cored wire with an effective amount of sulfur in the core.
 82. Anelectric arc welder as defined in claim 81 wherein said sulfur is in therange of 0.010 to 0.030 percent by weight of the electrode.
 83. Anelectric arc welder as defined in claim 13 wherein said cored wire is ametal cored wire with an effective amount of sulfur in the core.
 84. Anelectric arc welder as defined in claim 83 wherein said sulfur is in therange of 0.010 to 0.030 percent by weight of the electrode.
 85. Anelectric arc welder as defined in claim 12 wherein said cored wire is ametal cored wire with an effective amount of sulfur in the core.
 86. Anelectric arc welder as defined in claim 85 wherein said sulfur is in therange of 0.010 to 0.030 percent by weight of the electrode.
 87. Anelectric arc welder as defined in claim 11 wherein said cored wire is ametal cored wire with an effective amount of sulfur in the core.
 88. Anelectric arc welder as defined in claim 87 wherein said sulfur is in therange of 0.010 to 0.030 percent by weight of the electrode.
 89. Anelectric arc welder as defmed in claim 10 wherein said cored wire is ametal cored wire with an effective amount of sulfur in the core.
 90. Anelectric arc welder as defmed in claim 89 wherein said sulfur is in therange of 0.010 to 0.030 percent by weight of the electrode.
 91. Anelectric arc welder as defined in claim 9 wherein said cored wire is ametal cored wire with an effective amount of sulfur in the core.
 92. Anelectric arc welder as defined in claim 91 wherein said sulfur is in therange of 0.010 to 0.030 percent by weight of the electrode.
 93. Anelectric arc welder as defined in claim 1 wherein said pulse weldingprocess includes a succession of waveforms and said waveforms arecreated by a series of short current pulses generated at a frequencygreater than 18 kHz and with a profile controlled by a waveformgenerator.
 94. An electric arc welder as defined in claim 93 includingan interrupt circuit to interrupt said waveform upon occurrence of ashort circuit between said electrode and said workpiece.
 95. An electricarc welder as defined in claim 94 wherein a waveform profile of a plasmaboost pulse is processed by said welder during said interrupt.
 96. Anelectric arc welder as defined in claim 14 wherein said pulse weldingprocess includes a succession of waveforms and said waveforms arecreated by a series of short current pulses generated at a frequencygreater than 18 kHz and with a profile controlled by a waveformgenerator.
 97. An electric arc welder as defined in claim 96 includingan interrupt circuit to interrupt said waveform upon occurrence of ashort circuit between said electrode and said workpiece.
 98. An electricarc welder as defined in claim 97 wherein a waveform profile of a plasmaboost pulse is processed by said welder during said interrupt.
 99. Anelectric arc welder as defined in claim 8 wherein said pulse weldingprocess includes a succession of waveforms and said waveforms arecreated by a series of short current pulses generated at a frequencygreater than 18 kHz and with a profile controlled by a waveformgenerator.
 100. An electric arc welder as defined in claim 99 includingan interrupt circuit to interrupt said waveform upon occurrence of ashort circuit between said electrode and said workpiece.
 101. Anelectric arc welder as defined in claim 100 wherein a waveform profileof a plasma boost pulse is processed by said welder during saidinterrupt.
 102. An electric arc welder as defined in claim 5 whereinsaid pulse welding process includes a succession of waveforms and saidwaveforms are created by a series of short current pulses generated at afrequency greater than 18 kHz and with a profile controlled by awaveform generator.
 103. An electric arc welder as defined in claim 102including an interrupt circuit to interrupt said waveform uponoccurrence of a short circuit between said electrode and said workpiece.104. An electric arc welder as defined in claim 103 wherein a waveformprofile of a plasma boost pulse is processed by said welder during saidinterrupt.
 105. A method of pulse welding by a series of pulses betweenan advancing electrode and a workpiece, said method comprising: (a)detecting a short circuit between said electrode and said workpiece;and, (b) creating a plasma boost pulse after said short circuit.
 106. Amethod as defined in claim 105 further including: (c) clearing saidshort circuit before said plasma boost circuit.
 107. A method as definedin claim 106 wherein said plasma boost pulse has a regulated power inthe general range of 5-20 KW.
 108. A method as defined in claim 105wherein said plasma boost pulse has a regulated power in the generalrange of 5-20 KW.
 109. A method as defined in claim 108 wherein saidplasma boost pulse has a duration of 0.2-0.5.0s.
 110. A method asdefined in claim 107 wherein said plasma boost pulse has a duration of0.2-0.5.0s.
 111. A method as defined in claim 106 wherein said plasmaboost pulse has a duration of 0.2-0.5.0s.
 112. A method as defined inclaim 105 wherein said plasma boost pulse has a duration of 0.2-0.5.0ms.
 113. A method as defined in claim 112 wherein said electrode is acored wire.
 114. A method as defined in claim 111 wherein said electrodeis a cored wire.
 115. A method as defined in claim 110 wherein saidelectrode is a cored wire.
 116. A method as defined in claim 109 whereinsaid electrode is a cored wire.
 117. A method as defined in claim 108wherein said electrode is a cored wire.
 118. A method as defined inclaim 107 wherein said electrode is a cored wire.
 119. A method asdefined in claim 106 wherein said electrode is a cored wire.
 120. Amethod as defined in claim 105 wherein said electrode is a cored wire.121. A method as defined in claim 120 wherein said power boost pulse isregulated arc current.
 122. A method as defined in claim 119 whereinsaid power boost pulse is regulated arc current.
 123. A method asdefined in claim 118 wherein said power boost pulse is regulated arccurrent.
 124. A method as defined in claim 117 wherein said power boostpulse is regulated arc current.
 125. A method as defined in claim 114wherein said power boost pulse is regulated arc current.
 126. A methodas defined in claim 113 wherein said power boost pulse is regulated arccurrent.
 127. A method as defined in claim 106 wherein said power boostpulse is regulated arc current.
 128. A method as defined in claim 105wherein said power boost pulse is regulated arc current.
 129. A methodas defined in claim 112 including creating a controlled backgroundcurrent segment following said plasma boost pulses.
 130. A method asdefined in claim 111 including creating a controlled background currentsegment following said plasma boost pulses.
 131. A method as defined inclaim 108 including creating a controlled background current segmentfollowing said plasma boost pulses.
 132. A method as defined in claim107 including creating a controlled background current segment followingsaid plasma boost pulses.
 133. A method as defined in claim 106including creating a controlled background current segment followingsaid plasma boost pulses.
 134. A method as defined in claim 105including creating a controlled background current segment followingsaid plasma boost pulses.
 135. An electric arc welder for pulse weldingby a series of output pulses between an advancing electrode and aworkpiece, said welder comprising: a circuit for creating a plasma boostcurrent pulse between said pulses, a first timer for starting saidoutput pulses at a given time and a second timer for creating saidplasma boost pulses at a given position between said current pulses.136. An electric arc welder as defined in claim 135 wherein said plasmaboost pulse has a regulated power of 5-20 KW.
 137. An electric arcwelder as defined in claim 136 wherein said plasma boost pulse has aduration of 0.2-0.5.0 ms.
 138. An electric arc welder as defined inclaim 135 wherein said plasma boost pulse has a duration of 0.2-0.5.0ms.
 139. An electric arc welder as defined in claim 138 wherein saidelectrode is a cored wire.
 140. An electric arc welder as defined inclaim 137 wherein said electrode is a cored wire.
 141. An electric arcwelder as defined in claim 136 wherein said electrode is a cored wire.142. An electric arc welder as defined in claim 135 wherein saidelectrode is a cored wire.
 143. An electric arc welder as defined inclaim 135 wherein said plasma boost pulse is by regulation of arccurrent.
 144. A method of pulse welding by a series of output pulsesbetween an electrode and a workpiece, said method comprising: creating aplasma boost pulse between said output pulses.
 145. A method as definedin claim 144 wherein said plasma boost pulse has a regulated power inthe general range of 5-20 KW.
 146. A method as defined in claim 145wherein said plasma boost pulse has a duration of 0.2-0.5.0 ms.
 147. Amethod as defined in claim 144 wherein said plasma boost pulse has aduration of 0.2-0.5.0 ms.
 148. A method as defined in claim 147 whereinsaid electrode is a cored wire.
 149. A method as defined in claim 146wherein said electrode is a cored wire.
 150. A method as defined inclaim 145 wherein said electrode is a cored wire.
 151. A method asdefined in claim 144 wherein said electrode is a cored wire.
 152. Anelectric arc welder for performing a pulse welding process by a currentbetween an advancing electrode and a workpiece, said welder having anoutput voltage and comprising: a short detecting circuit creating ashort signal upon occurrence of a short circuit between said advancingelectrode and said workpiece, a circuit to increase said current aftersaid signal to clear said short circuit and wherein said electrode is acored wire.
 153. An electric arc welder as defmed in claim 152 whereinsaid voltage is less than 25 volts.
 154. An electric arc welder asdefined in claim 153 wherein said voltage is in the general range of17-22 volts.
 155. An electric arc welder as defined in claim 154 whereinsaid cored wire is self shielding.
 156. An electric arc welder asdefined in claim 153 wherein said cored wire is self shielding.
 157. Anelectric arc welder as defined in claim 152 wherein said cored wire isself shielding.
 158. An electric arc welder for performing a pulsewelding process by a current between an advancing electrode and aworkpiece, said process including a series of successive waveforms eachhaving a pulse defmed by a peak current and a background currentportion, said welder comprising: a short detecting circuit creating ashort signal upon a short circuit between said advancing electrode andsaid workpiece and a circuit to create each pulse of one of saidwaveforms with the transition from said peak current to a current levelbelow said background current for a short time and then to saidbackground current to encourage short circuits after each of saidpulses.
 159. An electric arc welder as defined in claim 158 wherein saidwaveforms are created by a series of short current pulses generated at afrequency greater than 18 kHz and with a profile controlled by awaveform generator.
 160. An electric arc welder for performing a pulsewelding process by a current between an advancing electrode and aworkpiece, said welder comprising: a short detecting circuit creating ashort signal upon occurrence of a short circuit between said advancingelectrode and said workpiece and a boost circuit to create a plasmaboost pulse after creation of said short signal.
 161. An electric arcwelder as defined in claim 160 including a circuit to increase saidcurrent after said signal and before said plasma boost pulse to breaksaid short circuit.
 162. An electric arc welder as defined in claim 161including a premonition circuit to predict said break and a circuit toreduce said current and then activate said boost circuit when said breakis predicted.
 163. An electric arc welder as defined in claim 160wherein said plasma boost pulse has a regulated power of 5-20 KW. 164.An electric arc welder as defined in claim 163 wherein said plasma boostpulse has a duration of 0.2-5.0 ms.
 165. An electric arc welder asdefined in claim 161 wherein said plasma boost pulse has a regulatedpower of 5-20 KW.
 166. An electric arc welder as defined in claim 165wherein said plasma boost pulse has a duration of 0.2-5.0 ms.
 167. Anelectric arc welder as defined in claim 154 including a circuit tocontrol said current increase into a first and second increase slopebefore said short breaks.
 168. An electric arc welder as defined inclaim 165 including a circuit to control said current increase into afirst and second increase slope before said short breaks.
 169. Anelectric arc welder as defined in claim 161 including a circuit tocontrol said current increase into a first and second increase slopebefore said short breaks.
 170. An electric arc welder as defined inclaim 162 wherein said electrode is a cored wire.
 171. An electric arcwelder as defined in claim 170 wherein said cored wire is a metal coredelectrode with an effective amount of sulfur in said core.
 172. Anelectric arc welder as defined in claim 161 wherein said electrode is acored wire.
 173. An electric arc welder as defined in claim 172 whereinsaid cored wire is a metal cored electrode with an effective amount ofsulfur in said core.
 174. An electric arc welder as defined in claim 160wherein said electrode is a cored wire.
 175. An electric arc welder asdefined in claim 174 wherein said cored wire is a metal cored electrodewith an effective amount of sulfur in said core.
 176. A method ofwelding by a series of pulses between an advancing electrode and aworkpiece, said method comprising: (a) creating a short signal uponoccurrence of a short circuit between said advancing electrode and saidworkpieces and, (b) creating a plasma boost pulse between said electrodeand said workpiece after creation of said short signal.
 177. A method asdefmed in claim 176 further including: (c) increasing current after saidsignal and before said plasma boost pulse to clear said short circuit.178. A method as defmed in claim 177 wherein said plasma boost pulse hasa regulated power of 5-20 KW.
 179. A method as defined in claim 178wherein said plasma boost pulse has a duration of 0.2-5.0 ms.
 180. Amethod as defined in claim 176 wherein said plasma boost pulse has aregulated power of 5-20 KW.
 181. A method as defined in claim 176wherein said plasma boost pulse has a duration of 0.2-5.0 ms.
 182. Amethod as defined in claim 177 wherein said current is increased aftersaid signal and then decreased as said short circuit is being cleared.183. A method as defined in claim 182 wherein said electrode is a coredwire.
 184. A method as defined in claim 183 wherein said cored wire is ametal cored wire with an effective amount of sulfur in said core.
 185. Amethod as defined in claim 177 wherein said electrode is a cored wire.186. A method as defined in claim 185 wherein said cored wire is a metalcored wire with an effective amount of sulfur in said core.
 187. Amethod as defined in claim 176 wherein said electrode is a cored wire.188. A method as defined in claim 187 wherein said cored wire is a metalcored wire with an effective amount of sulfur in said core.
 189. Anelectric arc welder for performing a pulse welding process between anadvancing electrode and a workpiece with a waveform including a weldingcurrent with a succession of pulses each having a peak current and abackground current before and after said current pulse, said weldercomprising: a circuit to reduce said welding current below said 5background current upon completion of each pulse to force a shortcircuit, a short detecting circuit creating a signal upon occurrence ofa short circuit between said advancing electrode and said workpiece, anda boost circuit to create a plasma boost pulse after creation of saidshort circuit.
 190. An electric arc welder as defined in claim 189including a circuit to increase said current after said signal andbefore said plasma boost pulse.
 191. An electric arc welder as defmed inclaim 189 wherein said plasma boost pulse has a regulated power of 5-20KW.
 192. An electric arc welder as defmed in claim 189 wherein saidplasma boost pulse has a duration of 0.2-5.0 ms.
 193. An electric arcwelder as defmed in claim 189 wherein said electrode is a cored wire.194. An electric arc welder as defined in claim 193 wherein said coredwire is a metal cored wire with an effective amount of sulfur in thecore.
 195. An electric arc welder as defined in claim 194 wherein saidsulfur is in the range of 0.010 to 0.030 percent by weight of theelectrode.
 196. A method of pulse welding between and advancingelectrode and a workpiece with a welding current including a successionof pulses each having a peak current and a background current before andafter said current pulse, said method comprising: (a) reducing saidwelding current to below said background current after each of saidcurrent pulses to force a short circuit; (b) creating a signal upondetecting a short circuit; (c) clearing said short circuit upon creationof said signal; and, (d) creating a plasma boost pulse when said shortcircuit has been cleared.
 197. A method as defined in claim 196including preventing a short circuit during said peak current of saidpulses.
 198. A method as defined in claim 197 wherein said preventingact is by limiting the time of said peak current.
 199. A method asdefined in claim 196 wherein said plasma boost pulse has a regulatedpower of 5-20 KW.
 200. A method as defined in claim 199 wherein saidplasma boost pulse has a duration of 0.2-5.0 ms.
 201. A method asdefined in claim 196 wherein said plasma boost pulse has a duration of0.2-5.0 ms.
 202. A method as defined in claim 196 wherein said electrodeis a cored wire.
 203. A method as defined in claim 202 wherein saidcored wire is a metal cored wire with an effective amount of sulfur.204. A method as defined in claim 203 wherein said sulfur is in therange of 0.010 to 0.030 percent by weight of the electrode.
 205. Anelectric arc welder for performing a pulse welding process by a voltagedriven current between an advancing electrode and a workpiece, saidwelder having an output voltage and comprising: a short detectingcircuit creating a short signal upon occurrence of a short circuitbetween said advancing electrode and said workpiece, a circuit toincrease said current after said signal, and a boost circuit to create aplasma boost pulse after said short circuit has been cleared.
 206. Anelectric arc welder as defined in claim 205 wherein said plasma boostpulse has a regulated power of 5-20 KW.
 207. An electric arc welder asdefined in claim 205 wherein said plasma boost pulse has a duration of0.2-5.0 ms.
 208. An electric arc welder as defined in claim 205 whereinsaid electrode is a cored wire.
 209. An electric arc welder as defmed inclaim 205 wherein said plasma boost pulse is by regulation of arccurrent.
 210. An electric arc welder as defined in claim 205 whereinsaid plasma boost pulse is by regulation of arc voltage.
 211. Anelectric arc welder as defined in claim 205 wherein said plasma boostpulse is by regulation of arc power.
 212. An electric arc welder asdefined in claim 205 wherein said boost circuit creates a controlled,background segment following said plasma boost pulse.
 213. An electricarc welder as defined in claim 205 wherein said voltage is less than 25volts.
 214. An electric arc welder as defined in claim 205 wherein thearc length is less than 0.30 inches.
 215. An electric arc welder asdefined in claim 205 wherein said pulse welding process includes asuccession of waveforms and said waveforms are created by a series ofshort current pulses generated at a frequency greater than 28 kHz andwith a profile controlled by a waveform generator.
 216. An electric arcwelder as defined in claim 208 wherein said cored wire is a metal coredwire with an effective amount of sulfur in the core.
 217. An electricarc welder as defined in claim 216 wherein said sulfur is in the rangeof 0.010 to 0.030 percent by weight of the electrode.
 218. An electricarc welder for performing a pulse welding process by a voltage drivencurrent between an advancing electrode and a workpiece, said welderhaving an output voltage and comprising: a short detecting circuitcreating a first signal upon occurrence of a short circuit between saidadvancing electrode and said workpiece and a second signal when saidshort is cleared and a boost circuit to create a plasma boost pulseafter creation of said second signal.
 219. An electric arc welder asdefmed in claim 1 including a circuit to increase said current aftersaid first signal and before said plasma boost pulse.
 220. An electricarc welder as defined in claim 219 including a delay between said firstsign of an activation of said current increasing circuit.
 221. Anelectric arc welder as defined in claim 218 wherein said plasma boostpulse has a regulated power of 5-20 KW.
 222. An electric arc welder asdefined in claim 218 wherein said plasma boost pulse has a duration of0.2-5.0 ms.
 223. An electric arc welder as defined in claim 219 whereinsaid plasma boost pulse has a regulated power of 5-20 KW.
 224. Anelectric arc welder as defined in claim 219 wherein said plasma boostpulse has a duration of 0.2-5.0 ms.
 225. An electric arc welder asdefined in claim 218 wherein said plasma boost pulse is by regulation ofarc voltage.
 226. An electric arc welder as defined in claim 218 whereinsaid plasma boost pulse is by regulation of arc power.
 227. An electricarc welder as defined in claim 218 wherein said plasma boost pulse isregulated by a slope output characteristic.